Engineered　cementitious　composites　(ECCs)　are　a　type　of　high-ductility　material　with　excellent　crack-control　capacity　and　pseudo-strain-hardening　behaviour.　To　improve　the　seismic　performance　and　damage-tolerant　capacity　of　traditional　reinforced　concrete　(RC)　columns,　this　paper　proposes　an　innovative　ECC-RC　composite　column　with　a　cast-in-place　or　precast　ECC　shell　in　the　plastic-hinge　zone,　namely　the　ECC　shell-RC　column.　Based　on　finite　element　software　ABAQUS,　a　comprehensive　numerical　and　analytical　study　of　the　seismic　performance　of　the　ECC　shell-RC　column　was　conducted.　First,　three-dimensional　(3D)　nonlinear　finite　element　models　were　developed　and　validated　using　previous　experimental　results.　Subsequently,　the　influence　of　different　design　parameters　on　the　seismic　performance　of　this　type　of　column　was　systematically　investigated　via　finite　element　analysis,　including　the　ECC　height,　ECC　shell　thickness,　axial　compression　ratio,　and　material　parameters.　The　seismic　performance　of　the　ECC　shell-RC　column　with　optimized　design　parameters　subjected　to　actual　ground　motions　was　also　preliminarily　investigated.　Notably,　certain　important　design　principles　of　ECC　shell-RC　columns　were　established.　Furthermore,　the　theoretical　critical　height　and　thickness　of　the　ECC　shell　were　determined　based　on　a　theoretical　analysis　of　the　plastic-hinge　(PH)　forming　mechanism.